Removal of chlorophylls present in Stevia (Stevia rebaudiana Bertoni) extracts by activated carbon adsorption and precipitation with lime food grade

Abstract

In this study, adsorption capacity of activated carbon, and food grade calcium hydroxide (food grade lime) to remove color present in Stevia extract, was evaluated. Quantification of chlorophyll A, B and C was realized using Hansmann spectrophotometric method. Subsequently, activated carbon adsorption capacity on chlorophylls were measured followed by removal of color using lime on the same extract sample. The 10 min residence process with activated carbon in a 0.05 g per 100 ml sample, showed 43.30% of adsorbed chlorophylls. Adsorption process on activated carbon was adjusted to Langmuir model, with a maximum adsorption capacity of chlorophylls in monolayers of q_max = 6.038 gg^–1 and value of constant Langmuir of b = 159.413 gml^–1. After, 10 minutes residence time treatment using 10 g per 100 ml of lime on the same sample, resulted in a total of 70.30% of chlorophylls removed. Adsorption process with activated carbon was developed at 25 ºC, and adsorption isotherms were adjusted to Langmuir model.